1. Field of the Invention
The present invention generally relates to assembly of components using woven preforms and particularly relates to assembly of components into structural joints using Z-pins and woven preforms.
2. Description of the Prior Art
Typical methods known in the art for attaching a composite skin to a composite frame web include forming the web as an xe2x80x9cIxe2x80x9d or xe2x80x9cCxe2x80x9d shape, making them more complex and expensive to fabricate. The flanged sections are fastened to adjacent sections using methods similar to those used with metal components, for example, by using fasteners. However, use of the fasteners adds weight to the joints.
These joints also have difficulty withstanding out-of-plane loading. Typical remedies for this are thick laminate stack-ups using many layers of composite fabric and having large flange radii. While this reduces the tension forces between the layers of the flanged section, the result is a heavy joint, reducing the weight savings realized when using composites.
Z-pins have been used to join two composite, laminate components in the prior art. For example, U.S. Pat. No. 5,968,639 to Childress discloses inserting Z-pins into a first composite component to form a stubble at a bonding face, then curing the first component. An uncured second component is then bonded to the first component with the stubble extending into and among the fibers of the second component and through the bond line.
Several techniques have been developed for inserting the Z-pins into composites laminates. Many techniques, like that described in U.S. Pat. No. 5,919,413 to Avila, are based on using a compressible foam carrier to retain the Z-pins before insertion. The pins are held in an orientation that is generally perpendicular to the surface in which they are to be inserted and are located near the surface. A piston is used to drive the pins into the surface, compressing the foam carrier as the pins are inserted. Typically, one or more nylon peel plies are placed on the surface of the laminate prior to insertion to ensure a clean bond surface and to protect the pins before assembly. The peel plies are removed prior to assembly.
A method is provided for using a woven preform having a base and at least one leg extending from the base. The preform is used to assemble first and second composite laminate components formed from tape or fabric and a resin matrix. Z-pins are inserted into the first component prior to its being cured, forming a stubble extending above a surface of the first component. The uncured preform is placed on the surface of the first component, the stubble extending into the preform. The cured second component is attached to the preform. Over-wrap plies are optionally placed on the outer surfaces of preform. Adhesive is optionally placed between the preform and the first and second components. A vacuum bag and tooling are used while curing the preform to adhere the legs of the preform to the second component and the base of the preform to the first component.